Rosaramicin is a 16-membered-ring macrolide antibiotic that is produced by Micromonospora rosaria. It possess high activity against gram positive, gram negative, and anaerobic bacteria. In addition, it has been shown superior in its spectrum and potency of activity relative to erythromycin and other macrolide antibiotics in a number of clinical studies. Lastly and importantly, rosaramicin is well tolerated in man. The avowed purpose of this proposal is to carry out a total synthesis of this antibiotic utilizing new threo-selective aldol-lactonization chemistry developed in these laboratories together with chiral sub-units easily derived from (S)-(-)-malic acid and (D)-(+)-glucose--compounds which are readily available and relatively inexpensive.